Add just enough support for static key so that we can use it from
tracepoints. Tracepoints rely on `static_key_false` even though it is
deprecated, so we add the same functionality to Rust.
It is not possible to use the existing C implementation of
arch_static_branch because it passes the argument `key` to inline
assembly as an 'i' parameter, so any attempt to add a C helper for this
function will fail to compile because the value of `key` must be known
at compile-time.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
rust/kernel/arch/arm64/jump_label.rs | 34 ++++++++++++++++++++++++++++
rust/kernel/arch/loongarch/jump_label.rs | 35 +++++++++++++++++++++++++++++
rust/kernel/arch/mod.rs | 24 ++++++++++++++++++++
rust/kernel/arch/riscv/jump_label.rs | 38 ++++++++++++++++++++++++++++++++
rust/kernel/arch/x86/jump_label.rs | 35 +++++++++++++++++++++++++++++
rust/kernel/lib.rs | 2 ++
rust/kernel/static_key.rs | 32 +++++++++++++++++++++++++++
scripts/Makefile.build | 2 +-
8 files changed, 201 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/arch/arm64/jump_label.rs b/rust/kernel/arch/arm64/jump_label.rs
new file mode 100644
index 000000000000..5eede2245718
--- /dev/null
+++ b/rust/kernel/arch/arm64/jump_label.rs
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Arm64 Rust implementation of jump_label.h
+
+/// arm64 implementation of arch_static_branch
+#[macro_export]
+#[cfg(target_arch = "aarch64")]
+macro_rules! arch_static_branch {
+ ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
+ core::arch::asm!(
+ r#"
+ 1: nop
+
+ .pushsection __jump_table, "aw"
+ .align 3
+ .long 1b - ., {0} - .
+ .quad {1} + {2} + {3} - .
+ .popsection
+ "#,
+ label {
+ break 'my_label true;
+ },
+ sym $key,
+ const ::core::mem::offset_of!($keytyp, $field),
+ const $crate::arch::bool_to_int($branch),
+ );
+
+ break 'my_label false;
+ }};
+}
+
+pub use arch_static_branch;
diff --git a/rust/kernel/arch/loongarch/jump_label.rs b/rust/kernel/arch/loongarch/jump_label.rs
new file mode 100644
index 000000000000..8d31318aeb11
--- /dev/null
+++ b/rust/kernel/arch/loongarch/jump_label.rs
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Loongarch Rust implementation of jump_label.h
+
+/// loongarch implementation of arch_static_branch
+#[doc(hidden)]
+#[macro_export]
+#[cfg(target_arch = "loongarch64")]
+macro_rules! arch_static_branch {
+ ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
+ core::arch::asm!(
+ r#"
+ 1: nop
+
+ .pushsection __jump_table, "aw"
+ .align 3
+ .long 1b - ., {0} - .
+ .quad {1} + {2} + {3} - .
+ .popsection
+ "#,
+ label {
+ break 'my_label true;
+ },
+ sym $key,
+ const ::core::mem::offset_of!($keytyp, $field),
+ const $crate::arch::bool_to_int($branch),
+ );
+
+ break 'my_label false;
+ }};
+}
+
+pub use arch_static_branch;
diff --git a/rust/kernel/arch/mod.rs b/rust/kernel/arch/mod.rs
new file mode 100644
index 000000000000..14271d2530e9
--- /dev/null
+++ b/rust/kernel/arch/mod.rs
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Architecture specific code.
+
+#[cfg_attr(target_arch = "aarch64", path = "arm64")]
+#[cfg_attr(target_arch = "x86_64", path = "x86")]
+#[cfg_attr(target_arch = "loongarch64", path = "loongarch")]
+#[cfg_attr(target_arch = "riscv64", path = "riscv")]
+mod inner {
+ pub mod jump_label;
+}
+
+pub use self::inner::*;
+
+/// A helper used by inline assembly to pass a boolean to as a `const` parameter.
+///
+/// Using this function instead of a cast lets you assert that the input is a boolean, rather than
+/// some other type that can be cast to an integer.
+#[doc(hidden)]
+pub const fn bool_to_int(b: bool) -> i32 {
+ b as i32
+}
diff --git a/rust/kernel/arch/riscv/jump_label.rs b/rust/kernel/arch/riscv/jump_label.rs
new file mode 100644
index 000000000000..2672e0c6f033
--- /dev/null
+++ b/rust/kernel/arch/riscv/jump_label.rs
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! RiscV Rust implementation of jump_label.h
+
+/// riscv implementation of arch_static_branch
+#[macro_export]
+#[cfg(target_arch = "riscv64")]
+macro_rules! arch_static_branch {
+ ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
+ core::arch::asm!(
+ r#"
+ .align 2
+ .option push
+ .option norelax
+ .option norvc
+ 1: nop
+ .option pop
+ .pushsection __jump_table, "aw"
+ .align 3
+ .long 1b - ., {0} - .
+ .dword {1} + {2} + {3} - .
+ .popsection
+ "#,
+ label {
+ break 'my_label true;
+ },
+ sym $key,
+ const ::core::mem::offset_of!($keytyp, $field),
+ const $crate::arch::bool_to_int($branch),
+ );
+
+ break 'my_label false;
+ }};
+}
+
+pub use arch_static_branch;
diff --git a/rust/kernel/arch/x86/jump_label.rs b/rust/kernel/arch/x86/jump_label.rs
new file mode 100644
index 000000000000..383bed273c50
--- /dev/null
+++ b/rust/kernel/arch/x86/jump_label.rs
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! X86 Rust implementation of jump_label.h
+
+/// x86 implementation of arch_static_branch
+#[macro_export]
+#[cfg(target_arch = "x86_64")]
+macro_rules! arch_static_branch {
+ ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
+ core::arch::asm!(
+ r#"
+ 1: .byte 0x0f,0x1f,0x44,0x00,0x00
+
+ .pushsection __jump_table, "aw"
+ .balign 8
+ .long 1b - .
+ .long {0} - .
+ .quad {1} + {2} + {3} - .
+ .popsection
+ "#,
+ label {
+ break 'my_label true;
+ },
+ sym $key,
+ const ::core::mem::offset_of!($keytyp, $field),
+ const $crate::arch::bool_to_int($branch),
+ );
+
+ break 'my_label false;
+ }};
+}
+
+pub use arch_static_branch;
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index fbd91a48ff8b..fffd4e1dd1c1 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -27,6 +27,7 @@
extern crate self as kernel;
pub mod alloc;
+pub mod arch;
mod build_assert;
pub mod error;
pub mod init;
@@ -38,6 +39,7 @@
pub mod prelude;
pub mod print;
mod static_assert;
+pub mod static_key;
#[doc(hidden)]
pub mod std_vendor;
pub mod str;
diff --git a/rust/kernel/static_key.rs b/rust/kernel/static_key.rs
new file mode 100644
index 000000000000..32cf027ef091
--- /dev/null
+++ b/rust/kernel/static_key.rs
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Logic for static keys.
+
+use crate::bindings::*;
+
+/// Branch based on a static key.
+///
+/// Takes three arguments:
+///
+/// * `key` - the path to the static variable containing the `static_key`.
+/// * `keytyp` - the type of `key`.
+/// * `field` - the name of the field of `key` that contains the `static_key`.
+#[macro_export]
+macro_rules! static_key_false {
+ ($key:path, $keytyp:ty, $field:ident) => {{
+ // Assert that `$key` has type `$keytyp` and that `$key.$field` has type `static_key`.
+ //
+ // SAFETY: We know that `$key` is a static because otherwise the inline assembly will not
+ // compile. The raw pointers created in this block are in-bounds of `$key`.
+ static _TY_ASSERT: () = unsafe {
+ let key: *const $keytyp = ::core::ptr::addr_of!($key);
+ let _: *const $crate::bindings::static_key = ::core::ptr::addr_of!((*key).$field);
+ };
+
+ $crate::arch::jump_label::arch_static_branch! { $key, $keytyp, $field, false }
+ }};
+}
+
+pub use static_key_false;
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index efacca63c897..60197c1c063f 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -263,7 +263,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE
# Compile Rust sources (.rs)
# ---------------------------------------------------------------------------
-rust_allowed_features := new_uninit
+rust_allowed_features := asm_const,asm_goto,new_uninit
# `--out-dir` is required to avoid temporaries being created by `rustc` in the
# current working directory, which may be not accessible in the out-of-tree
--
2.45.2.803.g4e1b14247a-googOn Fri, Jun 28, 2024 at 01:23:31PM +0000, Alice Ryhl wrote:
> rust/kernel/arch/arm64/jump_label.rs | 34 ++++++++++++++++++++++++++++
> rust/kernel/arch/loongarch/jump_label.rs | 35 +++++++++++++++++++++++++++++
> rust/kernel/arch/mod.rs | 24 ++++++++++++++++++++
> rust/kernel/arch/riscv/jump_label.rs | 38 ++++++++++++++++++++++++++++++++
> rust/kernel/arch/x86/jump_label.rs | 35 +++++++++++++++++++++++++++++
> rust/kernel/lib.rs | 2 ++
> rust/kernel/static_key.rs | 32 +++++++++++++++++++++++++++
> scripts/Makefile.build | 2 +-
> 8 files changed, 201 insertions(+), 1 deletion(-)
So I really find the amount of duplicated asm offensive. Is is far too
easy for any of this to get out of sync.
> diff --git a/rust/kernel/arch/x86/jump_label.rs b/rust/kernel/arch/x86/jump_label.rs
> new file mode 100644
> index 000000000000..383bed273c50
> --- /dev/null
> +++ b/rust/kernel/arch/x86/jump_label.rs
> @@ -0,0 +1,35 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! X86 Rust implementation of jump_label.h
> +
> +/// x86 implementation of arch_static_branch
> +#[macro_export]
> +#[cfg(target_arch = "x86_64")]
> +macro_rules! arch_static_branch {
> + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> + core::arch::asm!(
> + r#"
> + 1: .byte 0x0f,0x1f,0x44,0x00,0x00
> +
> + .pushsection __jump_table, "aw"
> + .balign 8
> + .long 1b - .
> + .long {0} - .
> + .quad {1} + {2} + {3} - .
> + .popsection
> + "#,
> + label {
> + break 'my_label true;
> + },
> + sym $key,
> + const ::core::mem::offset_of!($keytyp, $field),
> + const $crate::arch::bool_to_int($branch),
> + );
> +
> + break 'my_label false;
> + }};
> +}
Note that this uses the forced 5 byte version, and not the dynamic sized
one. On top of that it hard-codes the nop5 string :/
Please work harder to not have to duplicate stuff like this.
NAK.
On Wed, Jul 31, 2024 at 7:05 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, Jun 28, 2024 at 01:23:31PM +0000, Alice Ryhl wrote:
>
> > rust/kernel/arch/arm64/jump_label.rs | 34 ++++++++++++++++++++++++++++
> > rust/kernel/arch/loongarch/jump_label.rs | 35 +++++++++++++++++++++++++++++
> > rust/kernel/arch/mod.rs | 24 ++++++++++++++++++++
> > rust/kernel/arch/riscv/jump_label.rs | 38 ++++++++++++++++++++++++++++++++
> > rust/kernel/arch/x86/jump_label.rs | 35 +++++++++++++++++++++++++++++
> > rust/kernel/lib.rs | 2 ++
> > rust/kernel/static_key.rs | 32 +++++++++++++++++++++++++++
> > scripts/Makefile.build | 2 +-
> > 8 files changed, 201 insertions(+), 1 deletion(-)
>
> So I really find the amount of duplicated asm offensive. Is is far too
> easy for any of this to get out of sync.
>
> > diff --git a/rust/kernel/arch/x86/jump_label.rs b/rust/kernel/arch/x86/jump_label.rs
> > new file mode 100644
> > index 000000000000..383bed273c50
> > --- /dev/null
> > +++ b/rust/kernel/arch/x86/jump_label.rs
> > @@ -0,0 +1,35 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +// Copyright (C) 2024 Google LLC.
> > +
> > +//! X86 Rust implementation of jump_label.h
> > +
> > +/// x86 implementation of arch_static_branch
> > +#[macro_export]
> > +#[cfg(target_arch = "x86_64")]
> > +macro_rules! arch_static_branch {
> > + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> > + core::arch::asm!(
> > + r#"
> > + 1: .byte 0x0f,0x1f,0x44,0x00,0x00
> > +
> > + .pushsection __jump_table, "aw"
> > + .balign 8
> > + .long 1b - .
> > + .long {0} - .
> > + .quad {1} + {2} + {3} - .
> > + .popsection
> > + "#,
> > + label {
> > + break 'my_label true;
> > + },
> > + sym $key,
> > + const ::core::mem::offset_of!($keytyp, $field),
> > + const $crate::arch::bool_to_int($branch),
> > + );
> > +
> > + break 'my_label false;
> > + }};
> > +}
>
> Note that this uses the forced 5 byte version, and not the dynamic sized
> one. On top of that it hard-codes the nop5 string :/
>
> Please work harder to not have to duplicate stuff like this.
I really didn't want to duplicate it, but it's very hard to find a
performant alternative. Is there any way we could accept duplication
only in the cases where an 'i' parameter is used? I don't have the
choice of using a Rust helper for 'i' parameters.
Perhaps one option could be to put the Rust code inside jump_label.h
and have the header file evaluate to either C or Rust depending on the
value of some #ifdefs?
#ifndef RUST_ASM
/* existing C code goes here */
#endif
#ifdef RUST_ASM
// rust code goes here
#endif
That way the duplication is all in a single file. It would also avoid
the need for duplicating the nop5 string, as the Rust case is still
going through the C preprocessor and can use the existing #define.
I'm also open to other alternatives. But I don't have infinite
resources to drive major language changes.
Alice
On Wed, Jul 31, 2024 at 11:34:13PM +0200, Alice Ryhl wrote:
> > Please work harder to not have to duplicate stuff like this.
>
> I really didn't want to duplicate it, but it's very hard to find a
> performant alternative. Is there any way we could accept duplication
> only in the cases where an 'i' parameter is used? I don't have the
> choice of using a Rust helper for 'i' parameters.
>
> Perhaps one option could be to put the Rust code inside jump_label.h
> and have the header file evaluate to either C or Rust depending on the
> value of some #ifdefs?
>
> #ifndef RUST_ASM
> /* existing C code goes here */
> #endif
> #ifdef RUST_ASM
> // rust code goes here
> #endif
>
> That way the duplication is all in a single file. It would also avoid
> the need for duplicating the nop5 string, as the Rust case is still
> going through the C preprocessor and can use the existing #define.
I suppose that is slightly better, but ideally you generate the whole of
the Rust thing from the C version. After all, Clang can already parse
this.
That said, with the below patch, I think you should be able to reuse the
JUMP_TABLE_ENTRY macro like:
JUMP_TABLE_ENTRY({0}, {1}, {2} + {3})
> I'm also open to other alternatives. But I don't have infinite
> resources to drive major language changes.
Yes, well, you all picked this terrible language full well knowing it
hated C/C++ and had not a single effort put into integration with
existing code bases.
I find it very hard to care for the problems you've created for
yourself.
---
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index cbbef32517f0..6cff7bf5e779 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -12,12 +12,12 @@
#include <linux/stringify.h>
#include <linux/types.h>
-#define JUMP_TABLE_ENTRY \
- ".pushsection __jump_table, \"aw\" \n\t" \
- _ASM_ALIGN "\n\t" \
- ".long 1b - . \n\t" \
- ".long %l[l_yes] - . \n\t" \
- _ASM_PTR "%c0 + %c1 - .\n\t" \
+#define JUMP_TABLE_ENTRY(l_yes, key, branch) \
+ ".pushsection __jump_table, \"aw\" \n\t" \
+ _ASM_ALIGN "\n\t" \
+ ".long 1b - . \n\t" \
+ ".long " __stringify(l_yes) "- . \n\t" \
+ _ASM_PTR " " __stringify(key) " + " __stringify(branch) " - . \n\t" \
".popsection \n\t"
#ifdef CONFIG_HAVE_JUMP_LABEL_HACK
@@ -26,7 +26,7 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
{
asm goto("1:"
"jmp %l[l_yes] # objtool NOPs this \n\t"
- JUMP_TABLE_ENTRY
+ JUMP_TABLE_ENTRY(%[l_yes], %c0, %c1)
: : "i" (key), "i" (2 | branch) : : l_yes);
return false;
@@ -40,7 +40,7 @@ static __always_inline bool arch_static_branch(struct static_key * const key, co
{
asm goto("1:"
".byte " __stringify(BYTES_NOP5) "\n\t"
- JUMP_TABLE_ENTRY
+ JUMP_TABLE_ENTRY(%[l_yes], %c0, %c1)
: : "i" (key), "i" (branch) : : l_yes);
return false;
@@ -54,7 +54,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
{
asm goto("1:"
"jmp %l[l_yes]\n\t"
- JUMP_TABLE_ENTRY
+ JUMP_TABLE_ENTRY(%[l_yes], %c0, %c1)
: : "i" (key), "i" (branch) : : l_yes);
return false;
On Thu, Aug 1, 2024 at 12:28 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Wed, Jul 31, 2024 at 11:34:13PM +0200, Alice Ryhl wrote:
>
> > > Please work harder to not have to duplicate stuff like this.
> >
> > I really didn't want to duplicate it, but it's very hard to find a
> > performant alternative. Is there any way we could accept duplication
> > only in the cases where an 'i' parameter is used? I don't have the
> > choice of using a Rust helper for 'i' parameters.
> >
> > Perhaps one option could be to put the Rust code inside jump_label.h
> > and have the header file evaluate to either C or Rust depending on the
> > value of some #ifdefs?
> >
> > #ifndef RUST_ASM
> > /* existing C code goes here */
> > #endif
> > #ifdef RUST_ASM
> > // rust code goes here
> > #endif
> >
> > That way the duplication is all in a single file. It would also avoid
> > the need for duplicating the nop5 string, as the Rust case is still
> > going through the C preprocessor and can use the existing #define.
>
> I suppose that is slightly better, but ideally you generate the whole of
> the Rust thing from the C version. After all, Clang can already parse
> this.
>
> That said, with the below patch, I think you should be able to reuse the
> JUMP_TABLE_ENTRY macro like:
>
> JUMP_TABLE_ENTRY({0}, {1}, {2} + {3})
Yeah, I think this can work. I will submit a follow-up patch that
removes the duplication soon.
Alice
On Fri, 28 Jun 2024 13:23:31 +0000 Alice Ryhl <aliceryhl@google.com> wrote: > Add just enough support for static key so that we can use it from > tracepoints. Tracepoints rely on `static_key_false` even though it is > deprecated, so we add the same functionality to Rust. > > It is not possible to use the existing C implementation of > arch_static_branch because it passes the argument `key` to inline > assembly as an 'i' parameter, so any attempt to add a C helper for this > function will fail to compile because the value of `key` must be known > at compile-time. > > Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Gary Guo <gary@garyguo.net> > --- > rust/kernel/arch/arm64/jump_label.rs | 34 ++++++++++++++++++++++++++++ > rust/kernel/arch/loongarch/jump_label.rs | 35 +++++++++++++++++++++++++++++ > rust/kernel/arch/mod.rs | 24 ++++++++++++++++++++ > rust/kernel/arch/riscv/jump_label.rs | 38 ++++++++++++++++++++++++++++++++ > rust/kernel/arch/x86/jump_label.rs | 35 +++++++++++++++++++++++++++++ > rust/kernel/lib.rs | 2 ++ > rust/kernel/static_key.rs | 32 +++++++++++++++++++++++++++ > scripts/Makefile.build | 2 +- > 8 files changed, 201 insertions(+), 1 deletion(-)
Hi Alice
On Fri, Jun 28, 2024 at 9:24 PM Alice Ryhl <aliceryhl@google.com> wrote:
>
> Add just enough support for static key so that we can use it from
> tracepoints. Tracepoints rely on `static_key_false` even though it is
> deprecated, so we add the same functionality to Rust.
>
> It is not possible to use the existing C implementation of
> arch_static_branch because it passes the argument `key` to inline
> assembly as an 'i' parameter, so any attempt to add a C helper for this
> function will fail to compile because the value of `key` must be known
> at compile-time.
>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
> rust/kernel/arch/arm64/jump_label.rs | 34 ++++++++++++++++++++++++++++
> rust/kernel/arch/loongarch/jump_label.rs | 35 +++++++++++++++++++++++++++++
> rust/kernel/arch/mod.rs | 24 ++++++++++++++++++++
> rust/kernel/arch/riscv/jump_label.rs | 38 ++++++++++++++++++++++++++++++++
> rust/kernel/arch/x86/jump_label.rs | 35 +++++++++++++++++++++++++++++
> rust/kernel/lib.rs | 2 ++
> rust/kernel/static_key.rs | 32 +++++++++++++++++++++++++++
> scripts/Makefile.build | 2 +-
> 8 files changed, 201 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/arch/arm64/jump_label.rs b/rust/kernel/arch/arm64/jump_label.rs
> new file mode 100644
> index 000000000000..5eede2245718
> --- /dev/null
> +++ b/rust/kernel/arch/arm64/jump_label.rs
> @@ -0,0 +1,34 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! Arm64 Rust implementation of jump_label.h
> +
> +/// arm64 implementation of arch_static_branch
> +#[macro_export]
> +#[cfg(target_arch = "aarch64")]
> +macro_rules! arch_static_branch {
> + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> + core::arch::asm!(
> + r#"
> + 1: nop
> +
> + .pushsection __jump_table, "aw"
> + .align 3
> + .long 1b - ., {0} - .
> + .quad {1} + {2} + {3} - .
> + .popsection
> + "#,
> + label {
> + break 'my_label true;
> + },
> + sym $key,
> + const ::core::mem::offset_of!($keytyp, $field),
> + const $crate::arch::bool_to_int($branch),
> + );
> +
> + break 'my_label false;
> + }};
> +}
> +
> +pub use arch_static_branch;
> diff --git a/rust/kernel/arch/loongarch/jump_label.rs b/rust/kernel/arch/loongarch/jump_label.rs
> new file mode 100644
> index 000000000000..8d31318aeb11
> --- /dev/null
> +++ b/rust/kernel/arch/loongarch/jump_label.rs
> @@ -0,0 +1,35 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! Loongarch Rust implementation of jump_label.h
> +
> +/// loongarch implementation of arch_static_branch
> +#[doc(hidden)]
> +#[macro_export]
> +#[cfg(target_arch = "loongarch64")]
> +macro_rules! arch_static_branch {
> + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> + core::arch::asm!(
> + r#"
> + 1: nop
> +
> + .pushsection __jump_table, "aw"
> + .align 3
> + .long 1b - ., {0} - .
> + .quad {1} + {2} + {3} - .
> + .popsection
> + "#,
> + label {
> + break 'my_label true;
> + },
> + sym $key,
> + const ::core::mem::offset_of!($keytyp, $field),
> + const $crate::arch::bool_to_int($branch),
> + );
> +
> + break 'my_label false;
> + }};
> +}
I have tested these patches on LoongArch and it works as expected.
Tested-by: WANG Rui <wangrui@loongson.cn>
Thanks,
-Rui
> +
> +pub use arch_static_branch;
> diff --git a/rust/kernel/arch/mod.rs b/rust/kernel/arch/mod.rs
> new file mode 100644
> index 000000000000..14271d2530e9
> --- /dev/null
> +++ b/rust/kernel/arch/mod.rs
> @@ -0,0 +1,24 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! Architecture specific code.
> +
> +#[cfg_attr(target_arch = "aarch64", path = "arm64")]
> +#[cfg_attr(target_arch = "x86_64", path = "x86")]
> +#[cfg_attr(target_arch = "loongarch64", path = "loongarch")]
> +#[cfg_attr(target_arch = "riscv64", path = "riscv")]
> +mod inner {
> + pub mod jump_label;
> +}
> +
> +pub use self::inner::*;
> +
> +/// A helper used by inline assembly to pass a boolean to as a `const` parameter.
> +///
> +/// Using this function instead of a cast lets you assert that the input is a boolean, rather than
> +/// some other type that can be cast to an integer.
> +#[doc(hidden)]
> +pub const fn bool_to_int(b: bool) -> i32 {
> + b as i32
> +}
> diff --git a/rust/kernel/arch/riscv/jump_label.rs b/rust/kernel/arch/riscv/jump_label.rs
> new file mode 100644
> index 000000000000..2672e0c6f033
> --- /dev/null
> +++ b/rust/kernel/arch/riscv/jump_label.rs
> @@ -0,0 +1,38 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! RiscV Rust implementation of jump_label.h
> +
> +/// riscv implementation of arch_static_branch
> +#[macro_export]
> +#[cfg(target_arch = "riscv64")]
> +macro_rules! arch_static_branch {
> + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> + core::arch::asm!(
> + r#"
> + .align 2
> + .option push
> + .option norelax
> + .option norvc
> + 1: nop
> + .option pop
> + .pushsection __jump_table, "aw"
> + .align 3
> + .long 1b - ., {0} - .
> + .dword {1} + {2} + {3} - .
> + .popsection
> + "#,
> + label {
> + break 'my_label true;
> + },
> + sym $key,
> + const ::core::mem::offset_of!($keytyp, $field),
> + const $crate::arch::bool_to_int($branch),
> + );
> +
> + break 'my_label false;
> + }};
> +}
> +
> +pub use arch_static_branch;
> diff --git a/rust/kernel/arch/x86/jump_label.rs b/rust/kernel/arch/x86/jump_label.rs
> new file mode 100644
> index 000000000000..383bed273c50
> --- /dev/null
> +++ b/rust/kernel/arch/x86/jump_label.rs
> @@ -0,0 +1,35 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! X86 Rust implementation of jump_label.h
> +
> +/// x86 implementation of arch_static_branch
> +#[macro_export]
> +#[cfg(target_arch = "x86_64")]
> +macro_rules! arch_static_branch {
> + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
> + core::arch::asm!(
> + r#"
> + 1: .byte 0x0f,0x1f,0x44,0x00,0x00
> +
> + .pushsection __jump_table, "aw"
> + .balign 8
> + .long 1b - .
> + .long {0} - .
> + .quad {1} + {2} + {3} - .
> + .popsection
> + "#,
> + label {
> + break 'my_label true;
> + },
> + sym $key,
> + const ::core::mem::offset_of!($keytyp, $field),
> + const $crate::arch::bool_to_int($branch),
> + );
> +
> + break 'my_label false;
> + }};
> +}
> +
> +pub use arch_static_branch;
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index fbd91a48ff8b..fffd4e1dd1c1 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -27,6 +27,7 @@
> extern crate self as kernel;
>
> pub mod alloc;
> +pub mod arch;
> mod build_assert;
> pub mod error;
> pub mod init;
> @@ -38,6 +39,7 @@
> pub mod prelude;
> pub mod print;
> mod static_assert;
> +pub mod static_key;
> #[doc(hidden)]
> pub mod std_vendor;
> pub mod str;
> diff --git a/rust/kernel/static_key.rs b/rust/kernel/static_key.rs
> new file mode 100644
> index 000000000000..32cf027ef091
> --- /dev/null
> +++ b/rust/kernel/static_key.rs
> @@ -0,0 +1,32 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! Logic for static keys.
> +
> +use crate::bindings::*;
> +
> +/// Branch based on a static key.
> +///
> +/// Takes three arguments:
> +///
> +/// * `key` - the path to the static variable containing the `static_key`.
> +/// * `keytyp` - the type of `key`.
> +/// * `field` - the name of the field of `key` that contains the `static_key`.
> +#[macro_export]
> +macro_rules! static_key_false {
> + ($key:path, $keytyp:ty, $field:ident) => {{
> + // Assert that `$key` has type `$keytyp` and that `$key.$field` has type `static_key`.
> + //
> + // SAFETY: We know that `$key` is a static because otherwise the inline assembly will not
> + // compile. The raw pointers created in this block are in-bounds of `$key`.
> + static _TY_ASSERT: () = unsafe {
> + let key: *const $keytyp = ::core::ptr::addr_of!($key);
> + let _: *const $crate::bindings::static_key = ::core::ptr::addr_of!((*key).$field);
> + };
> +
> + $crate::arch::jump_label::arch_static_branch! { $key, $keytyp, $field, false }
> + }};
> +}
> +
> +pub use static_key_false;
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index efacca63c897..60197c1c063f 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -263,7 +263,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE
> # Compile Rust sources (.rs)
> # ---------------------------------------------------------------------------
>
> -rust_allowed_features := new_uninit
> +rust_allowed_features := asm_const,asm_goto,new_uninit
>
> # `--out-dir` is required to avoid temporaries being created by `rustc` in the
> # current working directory, which may be not accessible in the out-of-tree
>
> --
> 2.45.2.803.g4e1b14247a-goog
>
>
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